Start by drying the raw chicken breasts with a paper towel, in order to soak up any extra moisture.
Cut the chicken into bite-sized cubes. You can do this by placing the chicken breast vertically to you and cutting it in half length-wise. Then slice it in half length-wise again. Turn it horizontally to you and cut it into 1-inch pieces.
Put the cubed chicken into a medium-sized bowl and season with salt and white ground pepper.
Separate the egg whites of one egg into a small bowl and whisk with a fork until frothy—about 1 minute.
Pour the egg whites into the bowl of chicken, add the ground white pepper, and mix together. Place in the fridge with plastic wrap until ready to stir-fry.
To make the sauce, combine the soy sauce, chicken broth, hoisin sauce, sesame oil, rice vinegar, honey, and gochugaru in a small bowl and mix well. Then, using a mini sifter, sift the cornstarch into the sauce until the whole 1 tbs. is used up. Make sure to quickly whisk the sauce as you sift the cornstarch. Then set it aside.
Next, cut the green beans in 1-2 inch pieces. Place in a bowl, rinse, and then set aside.
Cut the mushrooms into slices. Set aside.
Next, heat a pan with ¼ cup oil on high. Cast iron pans or woks are great for cooking stir fries, as they conduct heat really well and keep the food hot. However, if you don’t have either of those pans, a frying pan works great too.
Using tongs, spread the chicken across the pan creating an even layer. Sauté the chicken until slightly undercooked, about 3-5 minutes. You want the chicken to be slightly undercooked before you add the vegetables, because you will need time to cook the vegetables, but don’t want to overcook the chicken.
Then add the green beans and mushrooms and sauté for 3-5 minutes, or until fork tender.
Add the sauce and sauté for about 2 minutes or until the sauce thickens.
Take the pan off the heat, and turn off the burner. Serve with chopped scallions and a side of rice. Enjoy!